Renovate: When upating mypy, widen accepted version range (#879)

Change how Renovate bumps `mypy` dependency.

When updating to mypy 1.19, previously it would change `>=1.13,<1.19` -> `>=1.19,<1.20`.

With this change, it should change to `>=1.13,<1.20`.

Doc: https://docs.renovatebot.com/configuration-options/#rangestrategy

Author: intgr

.github/renovate.json

@@ -9,5 +9,9 @@
     "automergeSchedule": ["* * * * 2"]
   },
   "packageRules": [
+      {
+          "matchPackageNames": ["mypy"],
+          "rangeStrategy": "widen"
+      }
   ]
 }